Rotor-windings for alternating-current dynamo-electric machines.



Y L. J. HUNT. ROTOR WINDINGS FOR ALTBRNATING CURRENT DYNAMO ELECTRIC MACHINES.

APPLIGA'LION FILED AUG. 10, 1909.

1,057,061 Patented Ma1.25, 1913.

5 SHEETSSHEET 1.

L. T. HUNT. ROTOR WINDINGS FOR'ALTERNATING CURRENT DYNAMO ELEGTRIG MACHINES. APPLICATION FILED AUG. 10, 1909.

Patented Mar. 25, 1913.

L. J. HUNT. ALTERNATING CURRENT DYNAMO ELECTRIC MA AIPLIOATIQN FILED AUG. 10, 1909.

CHINES.

ROTOR WINDINGS FOR Patented Mar. 25, 1913.

5 SHEETSSHEET 4.

as 00 C76 C077 mac-Thaw L. J. HUNT. ROTOR WINDINGS FOR ALTERNATING GURRENT DYNAMO ELECTRIC MACHINES. APPLICATION FILED AUG. 10 1909.

1,057,061 Patented Mar. 25, 1913.

5 SHEETS-SHEET 5 WiFfsses Patent No. 15,711 of 1906, it

ATENT onnion.

COMPANY, A CORPGRATION OF NEW YORK.

noron-wmnmes Fen ALTERNATING-CURRENT DYNAMO-ELECTRIC MACHINES.

To all whom it may concern:

Be it known that I, LOUIS Jonn HUNT, a subject of the King of Great Britain, residing at Sandycroft, in the county of Flint, in the Principality of Vales, England, have invented certain new and useful Improve ments in Rotorindings for Alternating Current Dynamo Electric Machines, of which the following is a specification.

This invention relates to alternating current dynamoelectric machines of the type in which there are two windings or the equivalent of two w ndings on both the stator and rotor. Such machines are old'and it has heretofore been proposed to connect inachines of this character sothat they may be operated at one of three speeds; one speed being obtained by connecting one the stator windings to the source of supply and stator winding, or

short circuiting the other the the equivalent thereof, U] which case two rotor windings operate in concatc tion; and the other two speeds being obtained by connecting one or the other of the stator windings to. the source of supply and short circuiting one or the other of the windings on the secondary member by means of a set of collector rings. Gne machine otthis type is illustrated in my United States Patent Reissue No. 13,354, dated Jan. 9, 1912.

As I have heretofore shown in my British is possible to simplify the two windings on the rotor in such a manner as to considerably reduce the amount of copper in such windings, when the rotor windings operate in concatenation.

My present invention has for its object a further improvement of the rotor windings which, while still retaining all the advantages for the cascade connection as described in my British iatent No. 15,711 of 1906, permits the machine to be operated at either of the other speeds.

Briefly, my invention consists in adding lo the rotor windings oi"? the British patent above referred toot-her windings which are adapted to be connected in circuit when the motor operating at either of the two speeds resulting from contacting one or the other of the stator windings. or their equivalent, to the source of supply, these additional windings being so designed and connected that they operate eitectively for either of the two speeds.

Specification of Letters Patent. Application filed August 10, 1909.

i l l i .the winding of 7 winding of Fig. 11 with Patented Mar. 2.), 151133. i erial No. 512,193. I: m'i'i'fififiicn M k) as lin o My invention will best be understood from the following description taken in con nection with the accomlimnying drawings, in which- Figure 1 illustrates a rotor winding of the type shown in Fig. 1, adapted to give a and 2 poles at cascade speed, but modified by the addition of further bars and slip rings so as to have three normal speeds of rotation; Figs. 1, 1 and 1 are diagrams illustrating the method of combining separate pole windings into a composite winding having corresponding sets outv poles connected in concatenation at cascade speed as hereinafter explained; 2, 3 and a are key diagrams showin the connections of the wiodin s oi Fig. 1 Li er the three respective speeds; if 5 and t3, explained hereinafter, (fUl'lL to l igs. 8 and 9 of German patent spec lion No. 2' 6,533, and illustrate rcspcctir ly the bars of basal pole and Q pole winding on a rotor, and the resultant windir giving the same ell'ec'i, with redundant canceled, and bars used in certain slot carry resultantcurrents compounded of two currents ditl'ering in phase by degrees; Fig. 7 shows the resultant winking o't' (5, with further bars added in the vacant slots and slip rings connected thereto l 'ig. 8 is a keydiagrani explaiziiug the [low of currents in the winding of Fig. 7, when the slip rings are not connected; Fig. 9 shows with the slip rin' s ccnnected so to give the higher speed of rotation; Fig. 10 is a key diagram corresponding to Fig. 9; Fig. 11 shows a further simplified form of winding giving four poles and two pol-es respectively at cascade speed, and Fig. 12 is a key diagram correspending thereto showing the flow of currentat cascade speed; 'l ig. 13 shows the the slip rings conto give the higher speed of iotation; Fig. 1% is the key diagram CUl'l sponding to Fig. 13; Figs. 15 and 16 show a winding of the type illustrated in Figs. I l and l-l, but designed to give dos and l nected so as parallel connections oi two parts of Llll. winding as hereinafter explained.

When two machines are connected in cascade the rotors of .both machines are mount-- ed on the same shaft, and, as is well know;

a alternating current is supplied to the $121 the stator winding.

-nected to the rotor windings of the second machine mounted onthe same shath'and the connections are generally suchthat a rotating.

field is produced in the second rotor revolving in the opposite direction to the first field e. m the negative direction. This field acts inductively on the winding of the sec-- ond stator producing a correspondingfield, and the induced currents may. beregulated by inserting resistances between roiation of the comb that of a machinehav corresponding to the sum of thenumbers ration is equivalentto mg a number of poles of poles of the two machines. Ibis same ideahas been carried into practice in machines having one stator equivalent of two windings; The current is supplied in such cases to one winding on the stator which with part of the winding on the rotor or secondary member which is arranged to give the same number of poles. The currents flow from this part into the other part of the winding on the rotor developing a different number of poles rotating usually in an opposite direction to that in which the rotor is revolving. The second part of the rotor Winding acts inductively in relation to the second Winding on the stator which is arranged to have a corresponding number of poles.

Such machines as are described above are already well known and will need no further description here. An mprovement upon them has been introduced reccntly,this improvement consisting in the windings on the rotor and a reduction in the number or bars'required, by omitting from the two windings on the rotor any pairs of bars which would carry resulting currents flowing in opposite directions and neutralizing the magnetic effects of each other. In some cases also it has been proposed, wheretwo bars lie together and carry currents in two of three phases, that these two barsshould be replaced by a single bar carrying a current in the thirdphase which would obviously be equivalent magnetically. Such windings hare been described in the specification of British Patent No. 15711 of 1906 and ot German Patent- No. 206533. In order that the said windings may be understood without the necessity of referring to the specifications of the said patents, lowing supplementary description is given of these windings. For this purpose referthe parts of The normal speed, of

and one rotor each ofwhich is provided with two windings or the acts inductively in connection the folfor the second, and c. those tor the third.

The windin it will bc seen is mesh-connected. liQ. i shows a three-phase tourpcle. wind ng also with one conductor per pole per phase, eacli phase in this case being short-clrcuited, upon itself. The sign upon iach conductor indicates the direction of the current in that conductor at a particular instant. Fig. 1 shows the resulting winding on the rotorobtained by superiniposing the windings ot Figs, and lland omitting bars which neutralize the magnetic eliecis ob each other. By laying the winding of Fig. l.

over that (if Fig it will be seen that at three points therc' are pairs of .curren'ts which neutralize these can therefore be omitted. anaiiiing laa rs can bc connc sted up in any bars carrying each other. and The re suitable way. either shown with each phase short circuited'on itself, or in a mesh or connection.such that currents in the proper phase and direction shall ilow in the respective bars.

In the specification of 3 a 'lurtbcr u'ioditication con:--1...ting in substituting where nossiblc for two bars carrying currents apart in phase, a single bar of larg r section carrying a combined current having the same rcsultant magnetic. effect as the two separate currents. This is explained hereinafterwith reference to Figs. and 6 of the drawings. The invention can be applied to windings having any of the relative number of poles as defined below. in most cases in the following description windings giving the equivalent of four poles and two poles rcspectivcly when running at cascade speed will be illustrated and explained, but it is to be puderstood that these numbers of poles have been chosen for simplicity of descrip tion only, and in practice larger numbers of poles would generally be used, c. g. eight and four poles, or twelve and eight poles, which would give balanced forces on the rotor at all speeds of rotation; in fact for satisfactory working and symmetrical distribution of the forces the two numbers of polesfor the rotor winding must be such that when these numbers tire divided by their greatest common factor, the one divi-- dend must be odd and the other even while German Patent No. is dcscribci't the common factor itself must be greater than two. It is to be't'urther understood. that only the rotor windings are described here but these must be used with suital'ilc stator windings giving corresponding nun;- bers of poles. Stator windings suitable for this purpose have been described for ini and 0, the current will be dealt with, and in all tain ways stance in the specification of United States In all cases three phase currents will be the drawings the following convention will be made :Full lines will represent the one phase marked a, which will be assumed to be carrying current of the maximum value at the moment chosen while the two other phases marked Z) and 0 will be indicated respectively by chain dotted lines, and will be assumed to be carrying currents of half the maximum value at .the same instantl hence at a star connection between the three phases a, b, flowing in say at a, and dividing equally between 6 and 0 through which it flows out.- A further distinctive symbol is required for parts of the windings which are carrying no current when the connections are made in cersuch windings will, be indicated by crosses alternating with dots and plain dotted Referring now to Fig. 1, it will be seen known, these. windings each terminatingin slip rings-marked 12; The crosses on the circles representing the bars indicate currents flowing downward, and the'dots indicate currents flowing upward respectively.

Referring now to Fig. 2, it will-be seen that the three slip rings 11 are connected together through resistances 13 which may be cut out .while the slip rings 12 are left open so that no currents flow in the additional bars lying between the connections to the slip rings 11 and 152. The flow of currents in the bars is now exactly the same as in the winding shown in Fig. 1", and the speed is that of a cascade motor wound for 4 poles and 2 poles respectively. This is the lowest speed and corresponds to that of a simple motor having (3 poles upon it.

to slip rings marked Referring now to Fig. 3, it will be seen will now carry form for carrying out (if) so resistances 14 which can be cut out, and the flow of current is now as indicated in the diagram Fig. 1; and the rotor gives a poles only. The speed is therefore increased in the ratio of three to two as compared with the cascade speed.

Fig. 4 shows the connections for getting a third speed of rotation. In this case the slip rings 12 are directly connected or short-circuited by switch blades 14, while the resistances 13 which may be cut out, are connected between the slip rings 11. The connections on the stator will have been changed over in'well known manner, and the rotor ings as indicated by the arrows in the key diagram Fig. d, and giving only 2 poles; hence the speed of rotation will be double that for the connections shown in Fig. 3 and. three times that for the connections shown in Fig. 2. Evidently, if this winding were only required to have two normal speeds of rotation, 1 here could be a permanent cenuection instead of the three slip rings 11 with their resistances l3, and only the slip rings 12 with their resistances 14 would be required for getting the second speed.

Although the winding above described is simple to understand and can. be used in practice, yet it is not the most satisfactory this invention for various reasons. There is a good deal of magnetic leakage, and the magnetizing current required for running at cascade speed (F ig. 2) is twice that required for running at either of the other speeds. It is possible however to use windings in which the ratio of the currents required for the two speeds is less than two to one, and in which the (PR losses and magnetic leakage are also less than they would be with the winding above describe Figs. 5 to 10 showhow the better form of winding can he produced. Fig. 5 .shows the arrangementof the liars of two separate 3 phase windings giving respectively & poles and 2 poles on the rotor (rotating in opposite directions in the manner already understood). Fig. 6 shows the resultant winding with the pairs of bars omitted which in Fig. 5 neutralize the action of one another, so as to leave only one bar in certain of the slots. In the other slots two of the bars carry currents differing in phase by degrees (as explained below) in the original winding Fig. 5, and these have been replaced by a single bar (shown in Fig.6 by two bars bound together) carrying resultant current wh 1Cl1 is 1.78 times that for any single bar in the original winding, and gives the same effect magnetically as the two-bars which it replaces in the winding shown in Fig. 5. The resultant winding in Fi 6 is already known, and is described as all-cad stated in the specification of German Patent No. 2065-33.

current .fiowing in the wind- The bars at the bottom of the windings in the windings carrying the resultant (1.73 value) currents are ]Ol11Cl to the points of e mesh and unite in a star connection 25.

two normal Reterrmg to nding is modified to give eeds in the following way. Fig. 7, it will be seen that in each of the slots which carries only one bar in Fig. 6, two additional bars have been inserted, lying side by side, each of these being halt the section. of the other bars in the winding and insulated one from the'other. These bars are connected with the slip rings 15 on the one hand and on the other hand to the midpoints of the mesh portions of the winding of Fig. 6, as illustrated in the key diagram Fig. 8. When the slip rings are not connected together the flow of current in the windings is illustrated in Figs. 7 and 8. The bars carry currents in the same direction and phase as in Fig. (3 so that the rotor runs at the cascade speed corresponding to 'l and poles. When the slip rings 15'are connected together-'21s illustrated in Fig. 9 the additional bars now carry currents and the windings simply produce d poles on the rotor. Fig. 10 shows the flow of currents in this case.

Comparing the pairs of Figs. 7 and S, 9 and 10, the following will be noticed. lVith the connections as in 7 and S, the windings marked with two letters, which are con nected in star and are shown by double lines, carry currents which are the resultant of currents in two phases 60 degrees apart. The current in phase a flowing upward in any bar will be 120 degrees distant in phase from currents in phases 1) and c flowing downward in a parallel bar. It is however only 6.0 degrees in phase distant from current in either phase b or 0 flowing upward (or in the same direction as a) in any bar. Similarly, currents in the phases 6 and 0 flowing in opposite directions are only 60 degrees apart in phase. The center star-connected bars in Fig. 8 have the letters beside them indicating the two phases they are carrying at the moment chosen, and the directions of flow of currents-in these two phases, from which it will be seen what resultant current is being carried by each of these star connections. These resultant currents are 1.73 times the currents in the other bars as already explained. Now it will be seen that with the connections as in Figs. 9 and 10 none of the barsare carrying these resultant currents compounded of two currents 60 degrees apart in phase, but all the bars are carrying simple currents in one of the three principal phases, and the currents in the star-connected bars are twice asgreat as those in the other bars, as indicated by the two letters beside thesebars. The current A cording to the present invention this.

l l l l l l .of Figs. 9 and 10.

itself two or more times density therefore in the half width. bars, in the slots containing three bars, will be double the current density in the other normal bars.

Referring now to Figs. 11 and 14:. it will be seen how the winding can be further simplified and the use of half width bars can be entirely avoided; Fig. 11 shows a a pole and 2 pole winding in which the respective bars are carrying exactly the same currents as-the corresponding bars in Fig. 7, but the end connections are modified as shown, and there is now only one bar in each of the slots connected to the slip rings 16. The windings of these slip rings are as before connected to the midpoints of the mesh portions of the main winding, as is seen more clearly for instance in the key diagram Fig. 12. while the mid-portions of the winding which carry resultant (1.73 value) currents are connected in star at 25 as before. When the slip rings are not connected together and there is no current in the two added bars in series with each slip ring, the flow of current is as indicated in Figs. 11 and 12, wh ch is exactly equivalent as stated to the flow in Figs. 7 and 8, and the winding gives -1 poles and 2 poles. VJ hen the slip rings are connected however, as shown in Figs. 13 and 11, the flow of the currents is very much altered. There'are only two bars in each slot. and these are carrying currents in each case in the same, phase and direction so as to give exactly the same magnetic effect as Figs. 9 and 10 in so far as the number of poles is concerned. Each bar throughout the wind ing when connected as in Figs, 13 and 1 1, is carrying current of the same rootmean square value so that to give the same magnetic effect as the winding of Figs. 9 and 10 the R. M. S. current in each bar must be half as much again as the currents in the bars The (PR losses are in this case considerably reduced, the bars being all made of the proper size to carry the currents when flowing as in Figs. 13 and 14 z'. e. at the non-cascade speed.

In practical windings giving say 8 and 1 poles the design will be exactly the sanie as that above described, the winding repeating around the circunr ference of the rotor according to the number of poles chosen. There are two possible ways of connecting these sets of windings as i .will be evident, viz ;they may be connected "in 'series, or in parallel, depending on cirnonmetparallel. It will be seen howeva that the end connections are lengthy and complicated, and for larger machines the conncc tious can be made much simpler by arranging the duplicated sets as shown in Fig. 16, where 23 is a star connection to which one end of each coil is connected, while the other ends of the windings for each phase are brought out to pairs of points 20, 21 and 22, each of which pairs is attached to a slip ring. lt will be evident to any electrical engineer that either of the methods shown invFigs. 1501 lb can adopted according to circumstances, ac- I a E cording'to the numbers or poles required,

which may make it simpler to use one or other form of connection,

' it is to be noted that wherever in this specification one bar has been shown in the and referred to, obviously two or bars could be used, so that each pair of represent a coil or any miltiple wo bars per slot. This will be obvious to any electrical engineer. Again, it is to be noted that in any of the windings as hereinbefore described Where only one set oi slip rings has been referred to, which slip rings form one neutral point in the winding when'they are directly connected, there is always one other such neutral point at least in the winding, and "enerally several other such points, which have been shown as permanently connected. If required these connections may be opened out and brought to slip rings between which resistances can be inserted so as to enable the speed of rotation to be further controlled by the cutting out of these resistances. This modification will also be obvious to any electrician and need notbe upon. It is evident too, that by suitably arranging the connections, the windings could be made when cascade connected, to give the efiect of the difierence of their basal number ofp ol'es instead of their sum, it this should be required; it is already well-known how to do this, and no explanation ofit will be needed beyond the statement that in designing such a winding, the two initial windings on the rotor from which the redundant bars are to be canceled would be arranged so that their phases would rotate in the same directidn, and then the redundant bars would be left out, and bars connected to slip rings, as already explained, and carrying currrents in the appropriate phases, would be inserted in the slots in which spaces are left.

Although the invention has been de- 'scribed'as applied to the rotor windings of alternating current motors, it will be obvious that if for any reason the functions of the stationary and rotating members of the machine are interchanged, .the invention will be equally applicable to the member of coils in parallel further dwelt I which is then stationary land which corre sponds to the rotor or secondary member hereinbefore referred to; the term rotor as used in the description must be read to cover this use of the invention. Finally,l desire it to be understood that my invention is not limited to an alternating currentdynamo electric machine, the windings of which are arranged to be connected in concatenation, and that it may be used in a two speed alternating current motor, the rotor of which is adapted to run at either one or another speed corresponding to the numbers of poles of the stator winding, and ii aim in the appended claims to cover all such and other modifications which do not depart from the spirit and scope of my invention.

I declare that what I claim is]:

1. ln an alternating current electric motor having stationary and rotating members with wiudin on each member adapted to give two different cascade working,

'asal number of poles for the basal windings on one member being united together by omitting redundant conductor bars of the winding, the combination with the united winding so obtained, of further windings onthe same member adapted to be interconnectedwith said united windings in such a manner that the said windings operate together to give one of their basal pole numbers in place of the two cascade working pole numbers.

2. In an alternating current electric motor having stationary and rotating members with windings on each member adapted to give two different basal numbers of poles for cascade working, the basal windings on one member being united together omitting redundant the winding, the combination with the united winding so obtained, of further windings on the'same member, andwmeans for so connecting said further windings in circuit with said basal windings that the said wind ings operate together to give one of their basal pole numbers in place of the two cascade working pole numbers.

3. In an alternating current electric motor having stationary and rotating members with windings on each member adapted to give two different. basal numbers of poles for cascade working, the basal windings on one member being united together with the omission of redundant conductor bars of the windings, the combination with the united windings so obtained, of further windings adapted to'be interconnected in star between terminal points in the first winding, and means for so connecting said further windings in circuit with said basal windings that the said windings operate together to give one of the basal pole numbers in place of the two cascade working pole numbers.

conductor bars of 4 In an alternc current electric motor having stationary and rotating members with windings on each member adapted to give two different basal numbers of poles for cascade working, the basal windings on one member being united together with the omission of redundant conductor bars of the windings, and the replacement of pairs of bars lying together which carry currents 60 degrees apart in phase by single bars carrying a resultant currentcompounded of these two currents, the combination with the united windings so obtained, of further windings adapted to be interconnected in star between terminal points in the first winding and set oi slip rings connected to said further winding, and means for connecting said slip rings together whereby the flow of currents in the windings can be changed so as to produce one of the basal pole numbers in place of the two cascadeworking pole numbers.

in an alternating current electric motor having stationary and rotating members with windings on each member adapted to give two different basal numbers of poles for cascade-working the basal windings on one member being united together by omitting redundant conductor bars of the windings and by using single bars to replace any pairs of bars lying together and carrying currents 60 degrees apart in phase to produce a mesh connected winding having a star connection from the points of the mesh, the combination with the said united windings of further windings and means for connecting them in star with the mid-points of the mesh portions of the said united windings and a set of slip rings connected to said further windings, and means for connecting said slip rings together whereby the flow of currents can be altered and the windings can be caused to give one of the basal pole numbers in place of the two cascade-working pole numbers.

6. In an alternating current electric motor having stationary and rotating members with windings on each member adapted to give two ditlerent basal numbers of poles for cascadeworking, the basal windings on one member lying in slots therein and being united together by omitting redundant conductor bars of the windings and by using single bars to replace any pairs of bars lying together and carrying currents 60 degrees apart in phase to produce a mesh connected winding having a star connection from the points of tion with the said united windings of fun ther windings whose bars occupy the slots in which spaces are left by the omission of the said redundant bars 0' the basal windings, and means for connecting said further windings in star between themidpoints of the mesh portions of the said united windtor having its windings normally the mesh. the combina ings, and a set of slip rings connected to said further windings, and means for connecting said slip rings together whereby the flow of? currents can be altered and the windings can be caused to give one of the basal pole numbers in place of the t vo cascade-wort:- ing pole numbers.

'7. In combination with an induction moarranged to produce a cascade eli'ect of different basal numbers'ofpoles, and the secondary member carrying in the same slot only conductors producing a like resultant magnetic etlect, of additional windings carried by said secondary arranged to be interconnected with the normally connected windings to furnish additional paths for the flow of currents and causing a resultant magnetic ciiect corresponding to one of the basal numbers o1 poles, and means for connecting and disconnecting said additional windings.

8. In combination with an induction motor having its windings normally arranged to produce a cascade eiicct of diilerent basal numbers of poles, and the secondary member carrying in the same slot only conductors producing a like resultant magnetic eilcct, of additional windings carried by said secondary arranged to be interconnected with the normally connected windings to furnish additional paths for the flow of currents and causing a resultant magnetic effect corresponding to one of the basal numbers of poles, means for connecting the neutral points of said normally arranged windings, and means of said additional windings.

9. An induction motor comprising a secondary member having interconnected star and delta connecting windings arranged to produce sets of poles of different basal numbersnormally in concatenation at cascade speed, and an additional winding having symmetrical portions connected in star-arrangement with symmetrical intermediate points of said first-named windings, and means for connecting or disconnecting said additional winding.

10. An induction motor comprising a secondary member having windings arranged to produce sets of poles of different basal numbers normally connected in concatenation at cascade speed,and an additional winding having symn'ietrical portions thereof connected to neutral points in the first-named windings and to slip rings, and means for connecting or disconnecting said rings, said additional winding when connected furnishing additional paths for the flow of currents and causing a resultant magnetic efiect corresponding to one of said basal numbers of poles.

11. An induction motor comprising a secondary member having windings arranged to produce sets of poles of different basal for connecting the neutral pointsnumbers normally connected in cencatenation at cascade speed, and an additional winding having symmetrical portions connected in star arrangement with symmetrical intermediate points of said first-named windings.

12. In combination With an induction m0- tor having its windings arranged to produce different basal numbers of poles for cascade working, and the secondary member carry ing in the same slot only conductors pro ducing' alike resultant magnetic effect, of

"additional windings carried by. said secondary adapted to be interconnected with said first mentioned windings in such a manner'that the said windings operate to-' gether to give one or another ofthe basal number of poles.-

13. An induction motor comprising a secondary member having interconnected star and delta connected windings arranged to produce sets of poles of different basal numbers for cascade working: and an additional winding having symmetrical portions connected at one of their ends with symmetri symmetrical portions thereof connected to a symmetrical intermediate points in the first,

named winding'and to slip rings, and means for connecting said rings, said additional Winding ausing a resultant magnetic eil'ect corresponding to one or the other of said. basal number of poles dependiiig on the connections of the primary member.

In witness \vhereof, l I have hereunto signed my name this 28th day of July 1909,

in the presence of two subscribing witnesses. 4a

LOUIS JOHN HUNT.

lVitnesses Hnmnrr A. GILL, THOMAS S. SHILLINGTON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. G. 

